I don't drink coffee at all really. And with the stillness at the time I have been doing light activities like walking my dog and the pain was profound immediately.
That can actually come from your diet, such as drinking coffee or other drinks that contain caffeine. Do you regularly have a cup of coffee at a certain time of day? It also can be that at the same time of day you notice sore breasts because that is when you're more still (for example, some people are more conscious of muscle soreness once they go to bed, even if it was there all day.)